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Hormonal medicines and periods

Hormonal contraception and periods

Some forms of hormonal contraception (for example the oral contraceptive pill, IUS coil, and injection may affect your menstrual cycle. This could cause your periods to change in frequency or flow.

Usually, oral contraceptive pills will make your periods lighter. You may find that your periods are irregular and the flow changes while your cycle adjusts to the changing hormones. After taking the pill for around six months, your periods should have formed a regular routine, so you will be better able to plan when they are due. Some women have also reported that their periods stop completely while taking the contraceptive pill.

Hormonal injections can also cause your periods to be irregular for a while before your body adjusts to the hormones. Some women report heavier periods when they start receiving hormonal injections, although periods usually become much lighter and less regular over time.

The IUS (Mirena) coil may also affect your periods. If your coil has been fitted in the last six months, you may experience some irregular bleeding or spotting (light bleeding at an irregular time of your cycle). After the initial six months, many women find that their periods completely stop. Some also say their periods become much lighter or irregular. This is quite common and nothing to worry about.

HRT and periods

Hormone Replacement Therapy (HRT) is a form of medicine that’s used by some women at the start of the menopause. It replaces the hormones that your body naturally stops making when you start the menopause.

You can find out more about this by reading our menopause advice.

Looking after yourself

Exercise and dieting

To have a regular period, you need to consume a certain amount of calories and have at least 16% body fat. Without this, it is hard for the ovaries to produce oestrogen and your periods can stop. Even if your periods stop, you still need to use contraception because there is still a chance you could become pregnant.

If you are exercising or dieting excessively before or during puberty, your first period may be late starting. If you have had a period before, you may find that your periods will stop, especially if you are limiting your food intake.

The recommended daily calorie intake for a woman is 2,000 calories. Exercising and limiting your food intake causes the ovaries to stop producing oestrogen. This can result in your periods stopping.

If your period has stopped for 6 months or more, you are preventing your bones from getting stronger (your bones will continue to grow until you are 30). This can cause osteoporosis (brittle bones) in middle age.

Absent or altered periods are not a normal part of exercise training, and signify that the body is under too much stress and doesn’t have enough energy to function properly. There are many risks involved with this, including:

  • weakening of your bones
  • infertility
  • increased risk of cardiovascular disease
  • endometrial cancer

If you think your periods have stopped as a result of exercise or dieting you should see your doctor.

You should also talk to your doctor who may want to discuss your medical history and may want to carry out some tests or a physical examination. Your doctor can also advise on ways to change your exercise and diet routine.

Absent or altered periods

  • If you suspect pregnancy to be the cause of your absent or altered periods testing kits are available to buy over the counter at your local pharmacy. (Alternatively you can see your doctor who can arrange relevant tests for you.
  • If you think your periods have stopped due to any medicines you are taking or because of hormonal contraception, you should discuss your concerns with either your doctor or the person who provided you with the medicine or contraception.
  • Make an appointment with your doctor if you have either a long term illness or think you may have a hormone imbalance or gynaecological condition that is affecting your periods.
  • Discuss treatment options with your doctor if you are trying for a baby but are finding it hard due to the unpredictability of your cycle.

Not sure what to do next?

If you are still concerned about hormonal medicines and periods, why not use healthdirect’s online Symptom Checker to get advice on when to seek medical attention.

The Symptom Checker guides you to the next appropriate healthcare steps, whether it’s self care, talking to a health professional, going to a hospital or calling triple zero (000).

Last reviewed: July 2015

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